Dielectric gapfill of high aspect ratio features utilizing a sacrificial etch cap layer

ABSTRACT

Methods and apparatuses for depositing material into high aspect ratio features, features in a multi-laminate stack, features having positively sloped sidewalls, features having negatively sloped sidewalls, features having a re-entrant profile, and/or features having sidewall topography are described herein. Methods involve depositing a first amount of material, such as a dielectric (e.g., silicon oxide), into a feature and forming a sacrificial helmet on the field surface of the substrate, etching some of the first amount of the material to open the feature opening and/or smoothen sidewalls of the feature, and depositing a second amount of material to fill the feature. The sacrificial helmet may be the same as or different material from the first amount of material deposited into the feature.

BACKGROUND

Semiconductor fabrication processes involve patterning operations,including depositing and etching of various materials on a semiconductorsubstrate. Substrates include features of various types, includinghorizontal and vertical features, negative features with slopedsidewalls, features with re-entrant features, and features made asnegative features in substrates having a multi-layered stack of two ormore materials such that the composition of the material on the surfaceof sidewalls of the feature varies depending on the depth of thefeature. Various techniques for filling such features exist, but asdevices shrink and features become smaller, feature fill without voidsor seams becomes increasingly challenging.

SUMMARY

Methods and apparatuses for processing semiconductor substrates areprovided herein. One aspect involves a method of filling a feature on asubstrate, the method including: providing the substrate including thefeature to a process chamber, the feature including a feature openingand sidewall topography, the sidewall topography including stubs on thesidewall of the feature; depositing a first amount of silicon oxide fora duration insufficient to fill the feature using a silicon-containingprecursor and an oxidant; exposing the first amount of the silicon oxideto an etchant to etch at least some of the first amount of the siliconoxide; and after etching the first amount of the silicon oxide,depositing a second amount of the silicon oxide over the etched firstamount of the silicon oxide.

In various embodiments, the stubs have a dimension perpendicular to aplanar surface of the sidewall of between 100 Å and about 300 Å.

In various embodiments, the duration insufficient to deposit the firstamount of silicon oxide into the feature forms an overburden of siliconoxide on a field surface of the substrate. In some embodiments, exposingthe first amount of the silicon oxide to the etchant includes etchingthe at least some of the first amount of the silicon oxide at or nearthe feature opening relative to the inside of the feature.

In various embodiments, the second amount of the silicon oxide isdeposited by plasma-enhanced chemical vapor deposition. In someembodiments, the method may also include, after depositing the secondamount of the silicon oxide, exposing the second amount of the siliconoxide to the etchant for a duration longer than the duration used forexposing the first amount of the silicon oxide to the etchant.

In some embodiments, the sidewalls of the feature include two or morematerials layered in a stack.

In various embodiments, the depositing of the first amount of thesilicon oxide and the exposing of the first amount of the silicon oxideto the etchant are performed without breaking vacuum. In variousembodiments, the depositing of the first amount of the silicon oxide andthe exposing of the first amount of the silicon oxide to the etchant areperformed in the same chamber.

In some embodiments, the exposing of the first amount of the siliconoxide to the etchant and the depositing of the second amount of thesilicon oxide are performed without breaking vacuum. In someembodiments, the exposing of the first amount of the silicon oxide tothe etchant and the depositing of the second amount of the silicon oxideare performed in the same chamber.

In various embodiments, the depositing of the first amount of thesilicon oxide, the exposing of the first amount of the silicon oxide tothe etchant, and the depositing of the second amount of the siliconoxide are performed without breaking vacuum. In various embodiments, thedepositing of the first amount of the silicon oxide, the exposing of thefirst amount of the silicon oxide to the etchant, and the depositing ofthe second amount of the silicon oxide are performed in the samechamber.

In various embodiments, the first amount of the silicon oxide isdeposited by one or more cycles of atomic layer deposition, each cycleof one or more cycles of the atomic layer deposition includingalternating pulses of the oxidant and the silicon-containing precursor.In various embodiments, the duration insufficient to fill the feature isthe duration for performing about 40 cycles or less of the atomic layerdeposition. In some embodiments, a plasma is ignited during the pulsesof the oxidant. In various embodiments, each cycle of one or more cyclesof the atomic layer deposition further includes purging the processchamber between the alternating pulses of the oxidant and thesilicon-containing precursor. In some embodiments, the process chamberis purged after depositing the first amount of silicon oxide and beforeexposing the first amount of the silicon oxide to the etchant. In someembodiments, the process chamber is purged after exposing the firstamount of the silicon oxide to the etchant and before depositing thesecond amount of the silicon oxide.

In various embodiments, the etchant is any one of nitrogen trifluoride(NF₃), fluoroform (CHF₃), octafluorocyclobutane (C₄F₈),tetrafluoromethane (CF₄), and combinations thereof.

In various embodiments, the feature has a depth of at least 5 microns.In various embodiments, the feature has an aspect ratio of at least15:1.

A method of filling a feature on a substrate, the method including:providing the substrate including the feature to a process chamber, thefeature including a feature opening and sidewall topography, thesidewall topography including stubs on the sidewall of the feature;depositing a first amount of silicon oxide for a duration insufficientto fill the feature using a silicon-containing precursor and an oxidant;after depositing the first amount of silicon oxide and prior to exposingthe first amount of silicon oxide to an etchant, depositing asacrificial helmet forming an overburden on a field surface of thesubstrate; exposing the substrate to the etchant to etch at least someof the first amount of the silicon oxide; and after etching the firstamount of the silicon oxide, depositing a second amount of the siliconoxide over the etched first amount of the silicon oxide to at leastpartially fill the feature.

In various embodiments, the stubs have a dimension perpendicular to aplanar surface of the sidewall of between 100 Å and about 300 Å.

In various embodiments, the sacrificial helmet is deposited by plasmaenhanced chemical vapor deposition.

In various embodiments, the sacrificial helmet includes silicon nitride.

In various embodiments, the sacrificial helmet includes silicon oxide.

In various embodiments, the depositing of the first amount of thesilicon oxide and the depositing of the sacrificial helmet are performedwithout breaking vacuum. In some embodiments, the depositing of thefirst amount of the silicon oxide and the exposing of the substrate tothe etchant are performed without breaking vacuum. In some embodiments,the depositing of the first amount of the silicon oxide, the depositingof the sacrificial helmet, and the exposing of the substrate to theetchant are performed without breaking vacuum. In some embodiments, theexposing of the substrate to the etchant and the depositing of thesecond amount of the silicon oxide are performed without breakingvacuum. In some embodiments, the depositing of the sacrificial helmet,the exposing of the substrate to the etchant and the depositing of thesecond amount of the silicon oxide are performed without breakingvacuum. In some embodiments, the depositing of the first amount of thesilicon oxide, the depositing of the sacrificial helmet, the exposing ofthe substrate to the etchant and the depositing of the second amount ofthe silicon oxide are performed without breaking vacuum.

In various embodiments, the depositing of the first amount of thesilicon oxide and the depositing of the sacrificial helmet are performedin the same chamber. In some embodiments, the depositing of the firstamount of the silicon oxide and the exposing of the substrate to theetchant are performed in the same chamber. In some embodiments, thedepositing of the first amount of the silicon oxide, the depositing ofthe sacrificial helmet, and the exposing of the substrate to the etchantare performed in the same chamber. In some embodiments, the depositingof the sacrificial helmet, the exposing of the substrate to the etchantand the depositing of the second amount of the silicon oxide areperformed in the same chamber. In some embodiments, the depositing ofthe first amount of the silicon oxide, the depositing of the sacrificialhelmet, the exposing of the substrate to the etchant and the depositingof the second amount of the silicon oxide are performed in the samechamber.

In various embodiments, the first amount of the silicon oxide isdeposited by one or more cycles of atomic layer deposition, each cycleof one or more cycles of the atomic layer deposition includingalternating pulses of the oxidant and the silicon-containing precursor.In various embodiments, the duration insufficient to fill the feature isthe duration for performing about 40 cycles or less of the atomic layerdeposition. In some embodiments, a plasma is ignited during the pulsesof the oxidant. In various embodiments, each cycle of one or more cyclesof the atomic layer deposition further includes purging the processchamber between the alternating pulses of the oxidant and thesilicon-containing precursor. In some embodiments, the process chamberis purged after depositing the first amount of silicon oxide and beforeexposing the first amount of the silicon oxide to the etchant. In someembodiments, the process chamber is purged after exposing the firstamount of the silicon oxide to the etchant and before depositing thesacrificial helmet.

In various embodiments, the etchant is any one of nitrogen trifluoride(NF₃), fluoroform (CHF₃), octafluorocyclobutane (C₄F₈),tetrafluoromethane (CF₄), and combinations thereof.

In various embodiments, the feature has a depth of at least 5 microns.In various embodiments, the feature has an aspect ratio of at least15:1.

Another aspect involves a method of filling a feature on a substrate,the method including: providing the substrate including the feature to aprocess chamber, the feature including a feature opening and sidewallshaving one or more reentrant surfaces; depositing a first amount of amaterial for a duration insufficient to fill the feature; exposing thefirst amount of the material to an etchant to etch at least some of thefirst amount of the material within the feature; and after etching thefirst amount of the material, depositing a second amount of the materialover the etched first amount of the material, whereby the material isany of silicon carbide, silicon nitride, silicon, tungsten, ruthenium,copper, cobalt, and molybdenum.

In various embodiments, the duration sufficient to deposit the firstamount of silicon oxide into the feature forms an overburden of siliconoxide on a field surface of the substrate.

In various embodiments, exposing the first amount of the silicon oxideto the etchant includes etching the at least some of the first amount ofthe silicon oxide at or near the feature opening relative to the insideof the feature.

In various embodiments, the second amount of the silicon oxide isdeposited by plasma-enhanced chemical vapor deposition.

In some embodiments, the method also includes, after depositing thesecond amount of the silicon oxide, exposing the second amount of thesilicon oxide to the etchant for a duration longer than the durationused for exposing the first amount of the silicon oxide to the etchant.

In various embodiments, the sidewalls of the feature include two or morematerials layered in a stack.

In various embodiments, depositing of the first amount of the siliconoxide and the exposing of the first amount of the silicon oxide to theetchant are performed without breaking vacuum.

In various embodiments, the exposing of the first amount of the siliconoxide to the etchant and the depositing of the second amount of thesilicon oxide are performed without breaking vacuum.

Another aspect involves a method of filling a feature on a substrate,the method including: providing the substrate including the feature to aprocess chamber, the feature including a feature opening and sidewalltopography, the sidewall topography including stubs on the sidewall ofthe feature; depositing a first amount of a first material for aduration insufficient to fill the feature; after depositing the firstamount of a first material and prior to exposing the first amount of thefirst material to an etchant, depositing a sacrificial helmet forming anoverburden on a field surface of the substrate, the sacrificial helmetincluding a second material; exposing the substrate to the etchant toetch at least some of the first amount of the first material; and afteretching the first amount of the first material, depositing a secondamount of the oxide over the etched first amount of the first materialto at least partially fill the feature.

In various embodiments, the stubs have a dimension perpendicular to aplanar surface of the sidewall of between 100 Å and about 300 Å.

In various embodiments, the first material is different from the secondmaterial. In various embodiments, the first material is compositionallythe same as the second material. In various embodiments, the secondmaterial is deposited by plasma enhanced chemical vapor deposition.

In various embodiments, the first material is deposited by atomic layerdeposition. In some embodiments, the second material is deposited byintroducing a silicon-containing precursor and a nitrogen-containingreactant simultaneously while igniting a plasma to form silicon nitride.In various embodiments, the nitrogen-containing reactant is introducedwith oxygen. In some embodiments, the etchant is a halogen-containingetchant. For example, in some embodiments, the etchant is nitrogentrifluoride. In various embodiments, the sacrificial helmet has etchselectivity relative to the first material when using the etchant. Insome embodiments, the etch selectivity of sacrificial helmet to thefirst material is between about 1:2 and about 1:5, where the firstmaterial etches about 2 to about 5 times faster than the sacrificialhelmet.

Another aspect involves an apparatus for processing a semiconductorsubstrate, the apparatus including: (a) at least one process chamber,the at least one process chamber including a pedestal for holding thesemiconductor substrate; (b) at least one outlet for coupling to avacuum; (c) one or more process gas inlets coupled to one or moreprocess gas sources; and (d) a controller for controlling operations inthe apparatus, including machine-readable instructions for: (i)introducing a silicon-containing precursor and an oxidant to deposit afirst amount of silicon oxide on the semiconductor substrate for aduration insufficient to fill a feature on the semiconductor substrate,the feature having a feature opening and sidewall topography, thesidewall topography having stubs on the sidewall of the feature; (ii)introducing an etchant to the at least one process chamber for aduration to etch at least some of the first amount of the silicon oxide;and (iii) after introducing the etchant to the at least one processchamber, introducing the silicon-containing precursor and the oxidant todeposit a second amount of silicon oxide over the etched first amount ofthe silicon oxide.

In various embodiments, the controller further includes instructions forsetting the duration of (iii) to be longer than the duration of (i). Invarious embodiments, the controller further includes machine-readableinstructions for performing (i) and (ii) without breaking vacuum.

In various embodiments, the apparatus also includes a plasma generatorfor generating a plasma. In some embodiments, the controller furtherincludes instructions for igniting the plasma when introducing theoxidant.

Another aspect involves an apparatus for processing a semiconductorsubstrate, the apparatus including: (a) at least one process chamber,the at least one process chamber including a pedestal for holding thesemiconductor substrate; (b) at least one outlet for coupling to avacuum; (c) one or more process gas inlets coupled to one or moreprocess gas sources; and (d) a controller for controlling operations inthe apparatus, including machine-readable instructions for: (i)introducing a deposition precursor and reactant for depositing a firstamount of a material for a duration insufficient to fill a feature onthe semiconductor substrate; (ii) introducing an etchant to etch atleast some of the first amount of the material in the feature; and (iii)after introducing the etchant, introducing the deposition precursor andthe reactant to deposit a second amount of the material over the etchedfirst amount of the material, whereby the material is any one of siliconcarbide, silicon nitride, silicon, tungsten, ruthenium, copper, cobalt,and molybdenum.

In various embodiments, the controller further includes instructions forsetting the duration of (iii) to be longer than the duration of (i). Invarious embodiments, the controller further includes machine-readableinstructions for performing (i) and (ii) without breaking vacuum.

In various embodiments, the apparatus also includes a plasma generatorfor generating a plasma. In some embodiments, the controller furtherincludes instructions for igniting the plasma when introducing theoxidant.

Another aspect involves an apparatus for processing a semiconductorsubstrate, the apparatus including: (a) at least one process chamber,the at least one process chamber including a pedestal for holding thesemiconductor substrate; (b) at least one outlet for coupling to avacuum; (c) one or more process gas inlets coupled to one or moreprocess gas sources; and (d) a controller for controlling operations inthe apparatus, including machine-readable instructions for: (i)introducing a silicon-containing precursor and an oxidant to deposit afirst amount of silicon oxide on the semiconductor substrate for aduration insufficient to fill a feature on the semiconductor substrate,the feature having a feature opening and sidewall topography, thesidewall topography having stubs on the sidewall of the feature; (ii)introducing one or more process gases for depositing a sacrificialhelmet forming an overburden on a field surface of the semiconductorsubstrate; (iii) introducing an etchant to the at least one processchamber for a duration to etch at least some of the first amount of thesilicon oxide; and (iv) after introducing the etchant to the at leastone process chamber, introducing the silicon-containing precursor andthe oxidant to deposit a second amount of silicon oxide over the etchedfirst amount of the silicon oxide.

In various embodiments, the controller includes instructions fordelivering a second silicon-containing precursor and anitrogen-containing reactant during (ii) to deposit the sacrificialhelmet, the sacrificial helmet including silicon nitride.

Another aspect involves an apparatus for processing a semiconductorsubstrate, the apparatus including: (a) at least one process chamber,the at least one process chamber including a pedestal for holding thesemiconductor substrate; (b) at least one outlet for coupling to avacuum; (c) one or more process gas inlets coupled to one or moreprocess gas sources; and (d) a controller for controlling operations inthe apparatus, including machine-readable instructions for: (i)introducing a first set of deposition precursors for depositing a firstmaterial to deposit a first amount of the first material on thesemiconductor substrate for a duration insufficient to fill a feature onthe semiconductor substrate; (ii) introducing one or more process gasesfor depositing a sacrificial helmet forming an overburden on a fieldsurface of the semiconductor substrate, the sacrificial helmet includinga second material; (iii) introducing an etchant to the at least oneprocess chamber for a duration to etch at least some of the first amountof the first material; and (iv) after introducing the etchant to the atleast one process chamber, introducing first set of depositionprecursors to deposit a second amount of the first material over theetched first amount of the first material.

In various embodiments, the first material is different from the secondmaterial. In various embodiments, the first material is compositionallythe same as the second material.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E are schematic illustrations of example substrates withfeatures of various types.

FIGS. 2A-2E are schematic illustrations of example substrates withfeatures of various types filled with material.

FIGS. 3A-3D are schematic illustrations of an example feature in asubstrate with a re-entrant feature undergoing feature fill.

FIGS. 4A-4D are schematic illustrations of an example feature in asubstrate with sidewall oscillations undergoing feature fill.

FIGS. 5A-5C are schematic illustrations of an example feature in asubstrate with a multi-layer stack undergoing feature fill.

FIGS. 6 and 7 are process flow diagrams depicting operations performedin methods performed in accordance with certain disclosed embodiments.

FIGS. 8A-8D are schematic illustrations of an example feature in asubstrate with a re-entrant feature undergoing feature fill inaccordance with certain disclosed embodiments.

FIGS. 9A-9D are schematic illustrations of an example feature in asubstrate with sidewall topography undergoing feature fill in accordancewith certain disclosed embodiments.

FIGS. 9E-9H are schematic illustrations of an example feature in asubstrate with sidewall topography undergoing feature fill in accordancewith certain disclosed embodiments.

FIGS. 10A-10C are schematic illustrations of an example feature in asubstrate with a multi-layer stack undergoing feature fill in accordancewith certain disclosed embodiments.

FIG. 11 is a timing schematic diagram depicting an example of operationsperformed in accordance with certain disclosed embodiments.

FIG. 12 is a schematic diagram of an example process chamber forperforming certain disclosed embodiments.

FIG. 13 is a schematic diagram of an example process tool for performingcertain disclosed embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Semiconductor fabrication processes often include dielectric gap fillusing chemical vapor deposition (CVD) and/or atomic layer deposition(ALD) methods to fill features. Described herein are methods of fillingfeatures with material, such as dielectric or metal material, includingbut not limited to silicon oxide, and related systems and apparatuses.The methods described herein can be used to fill vertical negativefeatures. Features formed in a substrate can be characterized by one ormore of narrow and/or re-entrant openings, constrictions within thefeature, and high aspect ratios. The substrate may be a silicon wafer,e.g., a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer, includingwafers having one or more layers of material such as dielectric,conducting, or semi-conducting material deposited thereon.

A feature may be formed in one or more of these layers. For example, afeature may be formed at least partially in a dielectric layer. A singlesubstrate as described herein includes multi-laminate stack having twoor more materials, such a ONON (oxide-nitride-oxide-nitride) stack, aOPOP (silicon oxide on polysilicon) stack, or OMOM stack (silicon oxideon metal such as tungsten, cobalt, or molybdenum) and features may beformed in such multi-layer substrates where sidewalls of the featuresinclude two or more compositions. Multi-laminate stacks may range from abilayer (such as ON) to 500 combined layers (such as {ON}₁₅₀). Featuresmay also have sloped sidewalls or sidewall topography. Sidewalltopography include jagged sidewalls having one or more stubs, each stubhaving a dimension perpendicular to a planar surface of the sidewall ofbetween 100 Å and about 300 Å. In various embodiments, sidewalltopography is characterized by two or more stubs where the two or morestubs are present on the sidewalls of a feature depth wise. That is, onestub on the sidewall is at a depth different than the depth at which thesecond stub is present on the sidewall. Additionally, features may alsoinclude a re-entrant profile.

A feature hole may also have a dimension near the opening, e.g., anopening diameter or line width, of between about 1 nm to about 1 micron,for example between about 25 nm to about 300 nm, such as about 200 nm. Afeature hole can be referred to as an unfilled feature or simply afeature. In some implementations, a feature hole may have an aspectratio of at least about 2:1, at least about 4:1, at least about 6:1, orat least about 20:1, or greater.

FIGS. 1A-1E show example substrates with features of various types. FIG.1A shows feature 102 a in a substrate having a multi-layer stackincludes two compositions 104 a and 114 a in alternating horizontallayers, where feature 102 a is defined by etching a hole into liner 106a. Note that while a liner 106 a is depicted in various examplesdescribed herein, in some embodiments a liner is not present. Where aliner is present, the liner may be a nitride material, such as but notlimited to silicon nitride, or in some embodiments, the liner may be apoly-silicon material.

FIG. 1B shows a feature 102 b in a substrate 104 b having straightsidewalls defined by liner 106 b. Feature 102 b of FIG. 1B has a highaspect ratio with straight sidewalls. FIG. 1C shows an example feature102 c in substrate 104 c with liner 106 c thereby forming feature 102 cwith positively sloped sidewalls where the feature opening 120 c at thetop of the feature 102 c is greater than the width at the bottom 112 c.FIG. 1D shows a feature 102 d in a substrate 104 d where the feature 102d is defined by etching a hole in liner 106 d, and the feature 102 dincludes negatively sloped sidewalls, or a re-entrant profile, where thefeature opening 120 d at the top of the feature 102 d is narrower thanthe width of the bottom 112 d of the feature 102 d. FIG. 1E shows afeature 102 e in a substrate 104 e where the feature 102 e is defined byetching a hole in liner 106 e, and the feature 102 e includes a sidewalltopography having stubs. In some cases, a feature can have sidewalltopography due to the type of etching performed to form the feature, orthe one or more materials in which the feature is formed. Gapfill offeatures such as these examples shown in FIGS. 1A-1E is dependent on thefeature type and profile. While existing techniques such as CVD and ALDmay be used to fill such features, conventional techniques result information of undesirable seams or voids within the feature.

FIG. 2A shows an example feature 202 a with liner 206 a in a substrateincluding a multi-layer stack having material 204 a and 214 a inalternating layers. Dielectric material 208 a is deposited into thefeature 202 a by conformal ALD, but a seam 210 a forms in the middle ofthe feature 202 a because dielectric material 208 a growth from thesidewalls meets in the middle of the feature 202 a, thereby forming theseam 210 a.

FIG. 2B shows a similar phenomenon for feature 202 b filled withdielectric material 208 b by ALD over liner 206 b defining the feature202 b having straight sidewalls in substrate 204 b. Likewise, in FIG.2C, the positively sloped feature 202 c including a narrower width atthe bottom 212 a in substrate 204 c with sidewalls defined by liner 206c also results in formation of seam 210 c when dielectric material 208 cis deposited by conformal ALD. FIG. 2D also shows a feature 202 d havingnegatively sloped features with a wider width at the bottom 212 ddefined by liner 206 d in substrate 204 d. In this example, a seam 210 dis still formed when dielectric material 208 d is deposited. In somecases, a void may also form at or near the bottom of the feature 202 ddue to the conformal fill by ALD. FIG. 2E shows an example of feature202 e having sidewall topography defined by liner 206 e in substrate 204e. The sidewall topography is characterized by stubs 216 e, and thebottom of the feature 212 e is wider than the width at the stubs 216 e.When material 208 e is deposited by ALD, microvoids 210 e form and thefeature is unable to be filled completely. Microvoids may be defined asvoids being less than about 50 nm in diameter, or in some embodimentsbetween about 30 nm and about 50 nm in diameter, or less than 30 nm indiameter, such as less than about 15 nm wide.

Some dep-etch-dep (deposition, etch, deposition) techniques have beenposited to fill various features with dielectric material. However,existing dep-etch-dep techniques also cause undesirable etching of othermaterial on the substrate, thereby resulting in material loss. Examplesare provided in FIGS. 3A-3D, 4A-4D, and 5A-5C as described below.

FIG. 3A shows an example of a feature 302 a in substrate 304 a where thefeature profile is defined by liner 306 a. As shown, the bottom of thefeature depicted at 312 a has a narrower width than a portion of thewidth at or near the feature opening, for which a re-entrant profile isdepicted. In conventional conformal ALD, material 308 b fills thefeature 302 b layer by layer as shown in FIG. 3B. In FIG. 3B, material308 b is depicted as being deposited into feature 302 b, the featureprofile of which is defined in liner 306 b of substrate 304 b. However,ALD deposition is conformal and results in the formation of void 310 b,while the bottom of the feature 312 b is completely filled. Conventionaldep-etch-dep involves etching after deposition of ALD, such as shown inFIG. 3C. In FIG. 3C, the deposited dielectric material 308 c is etchedback to open the narrow feature opening of feature 302 c in substrate304 c. However, even after the dielectric material 308 c is etched tothe surface of liner 306 c, void 310 c still remains while the opening308 c is not yet open. The bottom of the feature 312 c remains filled.In conventional dep-etch-dep, etch is performed until the feature isopened to allow further fill of the feature, and thus as shown in FIG.3D, etch back causes material loss 316 d of the liner 306 d to open thefeature 302 d and gain access to the void 310 d formed from priordeposition by ALD of material 308 d. The bottom of the feature 312 dremains filled in the substrate 308 d. However, such material loss 316 dis undesirable.

FIGS. 4A-4D also show an example of undesirable etching caused byconventional dep-etch-dep processes for filling features with dielectricmaterial. FIG. 4A includes a feature 402 a in substrate 404 a havingsidewall topography formed by etching in liner 406 a, the sidewalltopography having stubs where the feature width at the stubs is narrowerthan at the bottom 412 a of the feature. In such an embodiment, somestubs are at the same depth. In FIG. 4B, ALD is performed to depositdielectric material 408 b conformally into the feature 402 b over liner406 b. Note the space 410 b between deposited material on the sidewallsof the feature 402 b remains open and the material 408 b is depositedover stubs 416 b, including the bottom 412 b. However, to avoidformation of voids between sidewall topography, in FIG. 4C, thedeposited dielectric material 408 b is etched back to smoothen thedeposited material, as depicted by the smoothened surface 414 c ofmaterial 408 c. Note that the feature 402 c still includes roughdeposited material near the stubs 416 c and the bottom 412 c of thefeature 402 c of substrate 404 c. In FIG. 4D, the substrate 404 isfurther etched back to allow smoothening along the entire sidewall toreduce the formation of microvoids, as shown in the smoothening at thetop of the feature 414 d and the smoothening at the bottom of thefeature 416 d. Note that the dielectric material 408 d at or near thestubs 416 d and the bottom 412 d of the feature are smoothened such thatsubsequent deposition by ALD will not form microvoids. However, suchetch back resulted in material loss 416 d of the liner 406 d, whichcould thereby cause problems downstream.

FIGS. 5A-5C also show an example of a substrate having a multi-layerstack of two compositions 504 a and 514 a where the substrate includesfeatures 502 a with material 508 a deposited over liner 506 aconformally. In FIG. 5B, the material 508 b is etched back to open thefeature opening of features 502 b, but such etching results in etchingof liner 506 b, thereby resulting in a tapered profile. In subsequentdeposition of material 508 c in FIG. 5C, the material deposits over thetapered profile, the result being a substrate with filled features butwith material loss of the stack.

These and other issues with existing techniques result in undesiredfeature profiles for gapfill of high aspect ratio features and featureswith sidewall topography.

Provided herein are methods and apparatuses for depositing dielectricmaterial into features having high aspect ratios, sidewall topography,multi-layer stack compositions, and re-entrant profiles. Methods includemodulated dep-etch-dep durations and conditions to reduce and eliminateetching of a feature profile and underlayers of the substrate, includingdepositing a sacrificial helmet using plasma-enhanced chemical vapordeposition on the field surface of the substrate, thereby resulting inan overburden of material at the feature opening (which may be the sameas or different from the material being deposited in the feature) andperforming a longer etch back to open the feature while consuming onlythe sacrificial overburden of material without etching the underlyinglayers of the substrate and thus preventing etching of the featureprofile.

While the description below focuses on dielectric feature fill, aspectsof the disclosure may also be implemented in filling features with othermaterials. For example, feature fill using one or more techniquesdescribed herein may be used to fill features with other materialsincluding silicon-containing materials (e.g., silicon carbide, siliconnitride, silicon oxide, silicon) and metal-containing materials (e.g.,tungsten, ruthenium, copper, cobalt, molybdenum, nitrides and carbidesthereof).

FIG. 6 is a process flow diagram depicting operations of a methodperformed in accordance with certain disclosed embodiments. Operationsin FIG. 6 may be performed at a substrate temperature between about 50°C. and about 650° C.

In operation 602, a substrate is provided having features with sidewalltopography. For example, the features may have a profile such as thatdepicted in FIG. 1E. Although the example described with respect to FIG.6 is related to features with sidewall topography, it will be understoodthat in some embodiments, disclosed embodiments may be implemented onany one or more of high aspect ratio features with vertical sidewalls,features with re-entrant profiles, features with positively slopedsidewalls, features with negatively sloped sidewalls, and features withmulti-stack compositions on the sidewalls such as depicted in FIGS. 1B,1C, 1D, and 1A respectively. The substrate may be provided to a processchamber, which may be within a station of a single station ormulti-station apparatus for processing one or more wafers.

In operation 604, a first amount of dielectric material is deposited inthe features. In various embodiments, the first amount of dielectricmaterial is insufficient to fill the feature. An insufficiently filledfeature is defined as a feature having some dielectric materialdeposited therein and one or more voids present in the feature.Insufficiently filled features include features where material isdeposited along the sidewalls of the feature but the feature openingremains open. Deposition during operation 604 may be performed at achamber pressure between about 0.1 Torr and about 15 Torr, such as about6 Torr.

In various embodiments, the dielectric material is silicon oxide.Silicon oxide may be deposited by ALD, plasma-enhanced ALD (PEALD), CVD,or plasma-enhanced CVD (PECVD). ALD is a technique that deposits thinlayers of material using sequential self-limiting reactions. ALDprocesses use surface-mediated deposition reactions to deposit films ona layer-by-layer basis in cycles. As an example, an ALD cycle mayinclude the following operations: (i) delivery/adsorption of aprecursor, (ii) purging of the precursor from the chamber, (iii)delivery of a second reactant and optional plasma ignition, and (iv)purging of byproducts from the chamber. The reaction between the secondreactant and the adsorbed precursor to form a film on the surface of asubstrate affects the film composition and properties, such asnonuniformity, stress, wet etch rate, dry etch rate, electricalproperties (e.g., breakdown voltage and leakage current), etc.

In one example of an ALD process, a substrate surface that includes apopulation of surface active sites is exposed to a gas phasedistribution of a first precursor, such as a silicon-containingprecursor, in a dose provided to a chamber housing the substrate.Molecules of this first precursor are adsorbed onto the substratesurface, including chemisorbed species and/or physisorbed molecules ofthe first precursor. It should be understood that when a compound isadsorbed onto the substrate surface as described herein, the adsorbedlayer may include the compound as well as derivatives of the compound.For example, an adsorbed layer of a silicon-containing precursor mayinclude the silicon-containing precursor as well as derivatives of thesilicon-containing precursor. After a first precursor dose, the chamberis then evacuated to remove most or all of first precursor remaining ingas phase so that mostly or only the adsorbed species remain. In someimplementations, the chamber may not be fully evacuated. For example,the reactor may be evacuated such that the partial pressure of the firstprecursor in gas phase is sufficiently low to mitigate a reaction. Asecond reactant, such as an oxygen-containing gas, is introduced to thechamber so that some of these molecules react with the first precursoradsorbed on the surface. In some processes, the second reactant reactsimmediately with the adsorbed first precursor. In other embodiments, thesecond reactant reacts only after a source of activation such as plasmais applied temporally. The chamber may then be evacuated again to removeunbound second reactant molecules. As described above, in someembodiments the chamber may not be completely evacuated. Additional ALDcycles may be used to build film thickness.

In some implementations, the ALD methods include plasma activation. Asdescribed herein, the ALD methods and apparatuses described herein maybe conformal film deposition (CFD) methods, which are describedgenerally in U.S. patent application Ser. No. 13/084,399 (now U.S. Pat.No. 8,728,956), filed Apr. 11, 2011, and titled “PLASMA ACTIVATEDCONFORMAL FILM DEPOSITION,” which is herein incorporated by reference inits entirety.

For depositing silicon oxide, one or more silicon-containing precursorsmay be used. Silicon-containing precursors suitable for use inaccordance with disclosed embodiments include polysilanes(H₃Si—(SiH₂)_(n)—SiH₃), where n≥0. Examples of silanes are silane(SiH₄), disilane (Si₂H₆), and organosilanes such as methylsilane,ethylsilane, isopropylsilane, t-butylsilane, dimethylsilane,diethylsilane, di-t-butylsilane, allylsilane, sec-butylsilane,thexylsilane, isoamylsilane, t-butyldisilane, di-t-butyldisilane, andthe like.

A halosilane includes at least one halogen group and may or may notinclude hydrogens and/or carbon groups. Examples of halosilanes areiodosilanes, bromosilanes, chlorosilanes, and fluorosilanes. Althoughhalosilanes, particularly fluorosilanes, may form reactive halidespecies that can etch silicon materials when a plasma is struck, ahalosilane may not be introduced to the chamber when a plasma is struckin some embodiments, so formation of a reactive halide species from ahalosilane may be mitigated. Specific chlorosilanes aretetrachlorosilane, trichlorosilane, dichlorosilane, monochlorosilane,chloroallylsilane, chloromethylsilane, dichloromethylsilane,chlorodimethylsilane, chloroethylsilane, t-butylchlorosilane,di-t-butylchlorosilane, chloroisopropylsilane, chloro-sec-butylsilane,t-butyldimethylchlorosilane, thexyldimethylchlorosilane, and the like.

An aminosilane includes at least one nitrogen atom bonded to a siliconatom, but may also contain hydrogens, oxygens, halogens, and carbons.Examples of aminosilanes are mono-, di-, tri- and tetra-aminosilane(H₃Si(NH₂), H₂Si(NH₂)₂, HSi(NH₂)₃ and Si(NH₂)₄, respectively), as wellas substituted mono-, di-, tri- and tetra-aminosilanes, for example,t-butylaminosilane, methylaminosilane, tert-butylsilanamine,bis(tert-butylamino) silane (SiH₂(NHC(CH₃)₃)₂ (BTBAS), tert-butylsilylcarbamate, SiH(CH₃)—(N(CH₃)₂)₂, SiHCl—(N(CH₃)₂)₂, (Si(CH₃)₂NH)₃ andthe like. A further example of an aminosilane is trisilylamine(N(SiH₃)).

Additional reactants are also used during operation 604. For depositionof a silicon oxide helmet by PECVD, an oxidant is flowed to the processchamber with the silicon-containing precursor to react and depositsilicon oxide on the substrate. Example oxidants include oxygen gas,water, carbon dioxide, nitrous oxide, and combinations thereof. Invarious embodiments, the substrate is exposed to an oxidant and an inertgas simultaneously while the plasma is ignited. For example, in oneembodiment, a mixture of oxygen and argon is introduced to the substratewhile the plasma is ignited. Example inert gases include helium andargon. In some embodiments, the inert gas acts as a carrier gas todeliver the process gases to the substrate and is diverted upstream ofthe chamber. For deposition by ALD or PEALD, the silicon-containingprecursor and the reactant are introduced sequentially in pulses, whichmay be separated by purging operations. Such examples are furtherdescribed below with respect to FIG. 7.

In embodiments where a combination of any of ALD, PEALD, CVD, and PECVDare used to deposit the dielectric material in operation 604, the samereactants and precursors may be used during both techniques. In someembodiments, different precursors may be selected depending on thetechnique. For example, in some embodiments, ALD may be performed usinga halosilane, followed by PECVD using silane as the silicon-containingprecursor. In some embodiments, a plasma is ignited during one or moreof the techniques used to deposit the dielectric material.

In operation 607, a sacrificial helmet is deposited on a field surfaceof the substrate. A helmet is an overburden of material depositedpreferentially on the field surface of the substrate relative to theinterior of features on the substrate. In various embodiments, thehelmet is a sacrificial material used to cushion subsequent etchingprocesses so as to protect the underlying feature profile from beingetched or damaged.

In various embodiments, the helmet material grows on dielectric materialthat was deposited in operation 604 that remained on the field surfaceof the substrate. Thus, the sacrificial helmet does not close over thefeature opening and the feature opening remains open. In variousembodiments, the sacrificial helmet is deposited by PECVD. Thesacrificial helmet functions as a layer used to protect the underlyingsubstrate and feature profile during subsequent etching operation 608.The sacrificial helmet may be the same or different material as thedielectric material deposited into the features. For example, in someembodiments, the sacrificial helmet is a silicon oxide materialdeposited by PECVD while the material to be deposited into the featuresis also silicon oxide.

In some embodiments, the helmet is deposited to a thickness betweenabout 10 Å and about 500 Å. A helmet may be deposited using ALD, CVD, ora combination of both. In various embodiments, the helmet is depositedby PECVD. In various embodiments, the features are exposed to depositionprecursors for depositing a helmet (such as a silicon-containingprecursor and a nitrogen-containing precursor for depositing a siliconnitride helmet) for a duration sufficient to form the helmet. Theduration depends on the size of the feature opening, the depth of thefeature opening, the technique used to deposit the material, whether thematerial is the same as or different than the material deposited intothe feature, and, if the material is the same as the material beingdeposited into the feature, the amount of material, if any, alreadydeposited into the feature.

In some embodiments where the helmet material and the material beingdeposited into the feature are the same, the deposition of operation 604may continue in cycles to deposit the sacrificial helmet for operation607. In various embodiments, the deposition of operation 604 isperformed by PEALD or ALD, while operation 607 is performed by PECVD.Where the materials of the helmet and material to be deposited into thefeatures are the same, the same precursors may be used in both operation604 and operation 607. For example, any of the precursors and reactantsdescribed above with respect to operation 604 may be used for depositinga silicon oxide helmet in operation 607.

In some embodiments, the sacrificial helmet is a different material asthe material deposited into the features. For example, in someembodiments, the sacrificial helmet is a silicon nitride materialdeposited by PECVD while the material to be deposited into the featuresis silicon oxide. In various embodiments, the sacrificial helmet hasetch selectivity to the material to be deposited when exposed toetchants used in operation 608, such that etching in operation 608 doesnot damage the sacrificial helmet and the helmet can therefore withstandmany cycles of deposition and etch of the material to be deposited intothe feature. In some embodiments, the helmet is a silicon nitridematerial deposited by PECVD or PEALD using a silicon precursor andnitrogen plasma, simultaneously or in alternating pulses respectively.In various embodiments, formation of a silicon nitride helmet isperformed after silicon oxide is used to deposit the first amount ofsilicon oxide in the feature, and silicon nitride is deposited on thefield surface of the substrate. In various embodiments, silicon nitrideused as the helmet increases etch selectivity to the oxide duringetching. For deposition by CVD, the substrate may be exposed todeposition precursors (such as a silicon-containing precursor and anoxidant for depositing silicon oxide) for a duration between about 2seconds and about 120 seconds. In some embodiments, the helmet isdeposited using a plasma-enhanced process, such as PEALD or PECVD.

For deposition of a silicon nitride helmet by PECVD, anitrogen-containing gas such as nitrogen is flowed to the processchamber with a silicon-containing precursor to form silicon nitride. Invarious embodiments, nitrogen is ignited with a plasma to form siliconnitride.

In one example, silane is used as the silicon-precursor for performingPECVD of silicon nitride and/or silicon oxide. During deposition byPECVD, the precursor and reactants are flowed at various flow rates. Forexample, for depositing silicon oxide, silane may be flowed withnitrogen and/or nitrous oxide. Silane may be introduced at a flow ratebetween about 50 sccm and about 200 sccm, such as about 75 sccm.Nitrogen may be introduced at a flow rate between about 1000 sccm andabout 15000 sccm, such as about 3000 sccm. Nitrous oxide may beintroduced at a flow rate between about 5000 sccm and about 25000 sccm,such as about 20000 sccm.

In operation 608, the dielectric material is etched from featureopenings to leave a partially etched dielectric material in the feature.Etching may be performed for a duration sufficient to widen the featureopening such that subsequent deposition is capable of reaching thebottom of the feature. For example, in some embodiments etching isperformed for a duration between about 100 seconds and about 400seconds, such as about 115 seconds, or about 200 seconds, or about 300seconds, or about 400 seconds. In various embodiments, etching isperformed for a duration sufficient to open the feature opening withoutremoving material underlying the layers of the dielectric materialdeposited into the feature in operation 604. In various embodiments,etching is performed with etch selectivity to the helmet material. Forexample, in some embodiments, nitrogen trifluoride (NF₃) is the etchantused during operation 608 and the etch selectivity of silicon oxide to asacrificial silicon nitride helmet is between about 3:1 and about 5:1.

In some embodiments where operation 604 involves deposition of anoverburden or helmet, etching is performed such that the feature openingexposed while consuming some but not all of the helmet of sacrificialdielectric material on the field surface, thereby leaving a partiallyetched dielectric layer in the feature. Some of the helmet may beconsumed even if the helmet is a different material than that of thematerial to be deposited. However, in some embodiments, a helmet of adifferent material having etch selectivity to the material beingdeposited into the feature allows for the helmet to withstand longeretching times without being consumed as quickly as a helmet of the samematerial as the material being deposited would be etched under the sameprocess conditions. In some embodiments, a helmet of a differentmaterial having etch selectivity to the material being deposited intothe feature allows a thinner helmet to be deposited while stillmitigating etching of the feature profile.

The etchant selected depends on the material to be etched. For example,for etching silicon oxide, etching may be performed using afluorine-containing etch chemistry, such as by flowing nitrogentrifluoride (NF₃). Example etchants for etching silicon oxide includenitrogen trifluoride, fluoroform (CHF₃), octafluorocyclobutane (C₄F₈),tetrafluoromethane (CF₄), and combinations thereof. Example etchants foretching silicon carbide, silicon nitride, silicon, tungsten, ruthenium,copper, cobalt, and molybdenum for feature fill using these materialsinclude hydrobromic acid (HBr), fluoromethane (CH₃F), chlorine (Cl₂),silicon tetrafluoride (SiF₄), tetrafluoromethane (CF₄), borontrichloride (BCl), fluoroform (CHF₃) and combinations thereof.

In another example, for etching silicon carbide where silicon carbide isto be deposited into the features, etching may be performed usinghydrobromic acid, or CH₃F.

In another example, for etching silicon nitride where silicon nitride isto be deposited into the features, etching may be performed using CH₃F.

In various embodiments, etchants may be flowed with one or more carriergases, such as oxygen, nitrogen, and/or argon.

In various embodiments, a plasma is ignited during operation 608 toenhance etching. In some embodiments, the plasma is ignited using radiofrequency plasma. In some embodiments, a self-bias bias may be appliedto a powered pedestal holding the substrate during etch. In variousembodiments, the plasma is ignited while flowing the nitrogentrifluoride gas using a plasma power between about 1000 W and about 5000W. In various embodiments, the plasma is generated in-situ. In someembodiments, plasma may be generated remotely in a remote plasma chamberprior to delivering the process chamber housing the substrate.

In some embodiments, operations 604 and 608 are performed in differentchambers. In some embodiments, operations 604 and 608 are performed inthe same chamber. In some embodiments, operations 604 and 608 areperformed without breaking vacuum. For example, in some embodimentsoperations 604 and 608 are performed in separate stations in amulti-station chamber without breaking vacuum. Disclosed embodimentspromote efficiency since deposition and etching may be performed in thesame chamber or in the same tool.

In some embodiments, operation 608 may be performed to smooth thesidewalls. Disclosed embodiments may also be suitable for smootheningsidewalls during deposition into features having sidewall topographysuch that etching performed between depositions of dielectric materialis used to even out the surface and reduce the presence of stubs on thesidewalls of a feature. The etching may be performed by modulated theduration and plasma power to etch for a duration sufficient to smoothout the dielectric material deposited onto the sidewalls of the featurewithout exposing the underlying material on the substrate. Smootheningof sidewalls may be performed by etching for a duration of about 200seconds or less than about 200 seconds, or for a duration shorter thanwhich to open a feature opening.

In operation 610, a second amount of dielectric material is depositedover the partially etched dielectric material. In various embodiments,the second amount of dielectric material is deposited by ALD, PEALD,CVD, PECVD, or any combination thereof. Deposition may be performedusing any suitable precursors and reactants. For example, for depositinga second amount of silicon oxide, any silicon-containing precursordescribed above with respect to operation 604 may be used for operation610. Likewise, any suitable reactant for reacting with the precursor maybe used. For example, for depositing silicon oxide, an oxidant such asoxygen or nitrous oxide may be used to react with the silicon-containingprecursor. Any oxidant described above with respect to operation 604 maybe used in operation 610.

In some embodiments, the process chamber is purged between operation 604and operation 608. In some embodiments, the process chamber is purgedbetween operation 608 and 610. In some embodiments, the process chamberis purged after operation 610. Purging the chamber may involve flowing apurge gas or a sweep gas, which may be a carrier gas used in otheroperations or may be a different gas. Example purge gases include argon,nitrogen, hydrogen, and helium. In various embodiments, the purge gas isan inert gas. Example inert gases include argon, nitrogen, and helium.In some embodiments, purging may involve evacuating the chamber. In someembodiments, purging may include one or more evacuation subphases forevacuating the process chamber. Alternatively, it will be appreciatedthat purging may be omitted in some embodiments. Purging may beperformed for any suitable duration, such as between about 0.1 secondsand about 2 seconds.

In some embodiments, the second amount of the dielectric material fillsthe feature. In some embodiments, further operations are performed untilthe features are filled. For example, in some embodiments, operations604, 608, and 610 are repeated in cycles. In some embodiments, afterperforming operation 604, operations 608 and 610 are repeatedsequentially.

In some embodiments, operation 604 includes depositing a first amount ofdielectric features by ALD and depositing a helmet by PECVD and etchingin operation 608 is performed after deposition of the helmet. In someembodiments, the helmet is a different material than the dielectric usedto fill the feature. For example, in some embodiments, silicon oxide isdeposited in the features but silicon nitride is deposited as the helmetprior to etching. In some embodiments, using silicon nitride as thehelmet where the material to be deposited into the feature is siliconoxide may be used to achieve high etch selectivity of the siliconnitride sacrificial helmet material relative to the silicon oxidematerial during etching to prevent removal of the material deposited inthe feature. Additionally, use of a silicon nitride helmet may allowetching to be performed for a longer duration for less deposited siliconnitride, relative to using silicon oxide as a helmet. For example, forthe same deposited thickness of a silicon nitride helmet versus asilicon oxide helmet, the silicon oxide helmet will etch faster than asilicon nitride helmet. Thus, a thicker silicon oxide helmet is used toachieve a specified etching duration used to open a feature where athinner silicon nitride material is used.

FIG. 7 provides an example process flow diagram of an example methodperformed in accordance with certain disclosed embodiments. The exampleprocess in FIG. 7 includes repetitions of various operations such asoperations 604, 608, and 610 of FIG. 6.

In operation 701, a substrate having features with sidewall topographyis provided to a process chamber. Although the example described hereinrefers to features having sidewall topography, it will be understoodthat such embodiments can apply to substrates having features in amulti-laminate stack, features with positively sloped sidewalls,features with negatively sloped sidewalls, and features with re-entrantprofiles. Operation 701 may correspond to embodiments of operation 602described above with respect to FIG. 6.

In operations 702 a-1, 702 b-1, 702 c-1, and 702 d-1, a first amount ofdielectric material may be deposited into the features, and suchoperations may, in some embodiments, correspond to embodiments ofoperation 604 described above with respect to FIG. 6. In this specificexample, operations 702 a-1 through 702 d-1 may constitute one ALDcycle. In operation 702 a-1, the substrate is exposed to asilicon-containing precursor, such as any of those described above withrespect to operation 604, to adsorb the precursor onto the surface ofthe feature. In various embodiments, this operation is self-limiting. Insome embodiments, the precursor adsorbs to less than all of the activesites on the surface of the feature. In operation 702 b-1, the processchamber is optionally purged to remove any unadsorbed silicon-containingprecursors. In operation 702 c-1, the substrate is exposed to an oxidantand a plasma is ignited to form a first silicon oxide layer in thefeature. In various embodiments, this layer is the first amount ofdielectric material deposited in features referred to above in operation604 with respect to FIG. 6. In various embodiments, operation 702 c-1converts the adsorbed silicon-containing precursor layer to siliconoxide. In operation 702 d-1, the process chamber is optionally purged toremove byproducts from the reaction between the silicon-containingprecursor and the oxidant. Operations 702 a-1 through 702 d-1 may beoptionally repeated for two or more cycles as desired to deposit siliconoxide to a desired thickness in the feature.

In operation 708 a, the first amount of silicon oxide is partiallyetched from the feature. In various embodiments, this corresponds tooperation 608 of FIG. 6. Operation 708 a may be performed for a durationsufficient to open the feature opening. For example, in someembodiments, cycles of operations 702 a-1 through 702 d-1 may depositsilicon oxide into the feature until pinch-off, upon which operation 708a is performed to open the feature opening and thereby allow subsequentdeposition. Any etching chemistry as described above with respect tooperation 608 may be used. In some embodiments, a plasma is ignited tofacilitate etching. It will be understood that the etching chemistry andthe plasma conditions depend on the material being deposited in thefeatures. For example, for deposition of silicon oxide, operation 708 amay involve flowing nitrogen trifluoride and igniting a plasma at apower between about 1000 W and about 5000 W to etch silicon oxide.

In operation 710, the substrate is exposed to a silicon-containingprecursor and an oxidant to form a second amount of silicon oxide byPECVD. This may correspond to operation 610 of FIG. 6 as describedabove. In some embodiments, the silicon-containing precursor used is thesame as in operation 702 a-1. In some embodiments, thesilicon-containing precursor used is different from thesilicon-containing precursor used in 702 a-1. The selection of asilicon-containing precursor depends on the oxidant used and thetechnique (ALD, PEALD, CVD, PECVD, etc.) used. The oxidant may also bethe same as or different from the oxidant used in operation 702 c-1. Thesecond amount of silicon oxide may be used to deposit a helmet on thefield surface of the substrate.

In operation 708 b, the silicon oxide may be etched from the featureopening. This may correspond to a repeated operation of operation 608 ofFIG. 6 as described above. In some embodiments, the helmet deposited inoperation 710 protects the material underlying the silicon oxide and thefeature profile such that the helmet may be etched while etching thefeature opening relative to the interior of the feature. For example,etching the feature opening may involve etching the top 5% or top 10% ofthe depth of the feature. In some embodiments, due to the high aspectratio of the features, etching species may not reach the bottoms of thefeatures and thus, only the top up to about 50% of the materialdeposited in the feature is etched. Such etching may be modulated byusing a plasma power between about 1000 W and about 5000 W, for aduration between 2 seconds and about 200 seconds.

Operations 702 a-2 through 702 d-2 may constitute an ALD cycle. Suchexample shows the repeating of, for example, operation 604 of FIG. 6.Operation 702 a-2 may be the same as or involve the same precursors andconditions as operation 702 a-1, operation 702 b-2 may be the same as orinvolve the same purging conditions as operation 702 b-1, operation 702c-2 may be the same as or involve the same oxidant and/or plasmaconditions as operation 702 c-1, and operation 702 d-2 may be the sameas or involve the same purging conditions as operation 702 d-1. Duringoperation 702 a-2, the substrate is exposed to a silicon-containingprecursor to adsorb the precursor to the feature surface, which includessilicon oxide previously deposited and/or etched in prior operations. Insome embodiments, operations 702 a-1, 702 b-1, 702 c-1, 702 d-1, 708 a,710, 708 b, 702 a-2, 702 b-2, 702 c-2, and 702 d-2 may be optionallyrepeated until the features are filled.

FIGS. 8A-8D show an example of a substrate 804 a having a feature 802 awith a re-entrant feature defined by liner 806 a and a bottom of thefeature 812 a undergoing feature fill operations in accordance withcertain disclosed embodiments. In FIG. 8B, a first amount of siliconoxide 808 b is deposited over the substrate to form a helmet. Whilesilicon oxide is depicted as an example, in some embodiments, the helmetis silicon nitride, or silicon oxynitride. Due to the re-entrantprofile, a void 810 b is formed. This may correspond to deposition inoperation 604 of FIG. 6. In FIG. 8C, the substrate is etched back asshown in the etched silicon oxide 808 c. This may correspond tooperation 608 of FIG. 6. In FIG. 8D, the substrate etch back is completeand the feature is opened as shown with the exposed void 810 d, with nomaterial loss 816 d given the sacrificial helmet that was consumedduring etch back. The feature 802 d may now be filled with subsequentALD operations to deposit silicon oxide without having a void, ascompared to FIG. 3D.

FIGS. 9A-9D show an example of a substrate 904 a having a feature 902 awith a feature profile defined by liner 906 a with stubs 916 a and abottom of the feature 912 a undergoing feature fill operations inaccordance with certain disclosed embodiments. In FIG. 9B, a firstamount of silicon oxide 908 b is deposited over the substrate to form ahelmet as shown in the overburden deposited over the field surface ofthe liner 906 b. Due to the sidewall topography, there is space 910 bbetween the sidewalls of deposited silicon oxide. This deposition maycorrespond to deposition in operation 604 of FIG. 6. In FIG. 9C, thesubstrate is etched back as shown in the etched silicon oxide 908 c,resulting in smoothened surface 914 c. This may correspond to operation608 of FIG. 6. In FIG. 9D, the substrate etch back is complete and thefeature is opened and the sidewalls at 914 d and 916 d are bothsmoothened as shown, with no material loss 916 d given the sacrificialhelmet that was consumed during etch back. The feature 902 d may now befilled with subsequent ALD operations to deposit silicon oxide withouthaving a void, as compared to FIG. 4D.

FIGS. 9E-9H show an example of a substrate 904 e having a feature 902 ewith a feature profile defined by liner 906 e with stubs 916 e and abottom of the feature 912 e undergoing feature fill operations inaccordance with certain disclosed embodiments. In FIG. 9F, a firstamount of silicon oxide 908 f is deposited into the feature 902 f, and asilicon nitride helmet 999 f is deposited over the substrate as shown inthe overburden deposited over the field surface of the liner 906 f. Thisdeposition may correspond to deposition in operations 604 and 607 ofFIG. 6. Due to the sidewall topography, there is space 910 f between thesidewalls of deposited silicon oxide. In FIG. 9G, the substrate isetched back as shown in the etched silicon oxide 908 g, resulting insmoothened surface 914 g. This may correspond to operation 608 of FIG.6. Note that silicon nitride has etch selectivity to silicon oxide, somuch of the silicon oxide remains and the silicon nitride helmet canwithstand the etching operation for a longer duration; however sinceetch selectivity here is not necessarily infinite, some silicon nitridemay be removed during the etching process. In FIG. 9H, the substrateetch back is complete and the feature is opened and the sidewalls at 914h and 916 h are both smoothened as shown, with no material loss 916 hgiven the sacrificial helmet 999 h having etch selectivity relative tosilicon oxide. Note that in some embodiments, some of the helmet 999 hmay be removed but not as much as silicon oxide would, given the sameetching conditions. The feature 902 h may now be filled with subsequentALD operations to deposit silicon oxide without having a void, ascompared to FIG. 4D.

FIGS. 10A-10C show an example of a substrate with multi-laminate stackhaving two materials 1004 a and 1014 a with having a feature 1002 aundergoing feature fill operations in accordance with certain disclosedembodiments. A first amount of silicon oxide 1008 a is deposited overthe substrate to form a helmet. This may correspond to deposition inoperation 604 of FIG. 6. In FIG. 10B, the substrate is etched back asshown in the etched silicon oxide 1008 b. This may correspond tooperation 608 of FIG. 6. In FIG. 10C, the feature 1002 c is filled withsubsequent ALD operations to deposit silicon oxide without causingdamage to the feature profile, as compared to FIG. 5C.

FIG. 11 is a timing sequence diagram of example pulses in accordancewith an example of repeated operations of FIG. 6 using a combination ofPEALD and PECVD for depositing silicon oxide during depositionoperations. FIG. 11 shows phases in an example process 1100, for variousprocess parameters, such as carrier gas or purge gas flow,silicon-containing precursor flow, oxidant flow, plasma power, andetchant flow. The lines indicate when the flow or plasma power is turnedon and off. Other process parameters not shown in FIG. 11 may also berelevant for modulating certain disclosed embodiments; such parametersinclude, but are not limited to, flow rates for precursor, inert,reactant, and etchant gases, substrate temperature, and process chamberpressure.

Process 1100 includes ALD cycles 1102-1, etch phase 1108-1, ALD cycle1110-1, PECVD exposure phase 1110-2, long etch back phase 1108-2, andALD cycles 1102-2. Although a specific sequence of example operationsare shown in FIG. 11, it will be understood that this is an example andother variations of ALD, PECVD, and etching may be used for substrateswith features of various types and for various materials. Further, whileFIG. 11 shows silicon precursor and oxidant flows for depositing siliconoxide, it will be understood that embodiments may be suitable fordepositing any desired material such as described elsewhere herein.

ALD cycles 1102-1 include silicon-containing precursor exposure phase1102 a, purge phase 1102 b, oxidant exposure phase 1102 c, and purgephase 1102 d. In silicon-containing precursor exposure phase 1102 a,argon is flowed as a carrier gas with silicon-containing precursor gasflow on, while oxidant and etchant flows are off and the plasma isturned off. In purge phase 1102 b, argon gas remains on whilesilicon-containing gas, oxidant gas, and etchant gas flows are off andplasma is off. In oxidant exposure phase 1102 c, oxidant and purge gasflows are on, while plasma is turned on and silicon-containing precursorand etchant gas flows are off. In purge phase 1102 d, argon gas is onwhile silicon-containing gas flow, oxidant gas flow, and etchant gasflows are off and plasma is turned off. While one ALD cycle is depicted,it will be understood that multiple cycles may be performed in someembodiments.

Etch phase 1108-1 includes one etching phase 1108 a whereby argon gasand etchant gas flows are on and plasma is turned on, whilesilicon-containing precursor and oxidant gas flows are off.

In purge phase 1153 a, argon acts as a purge gas and argon gas flow isturned on, while silicon-containing precursor gas, oxidant gas, andetchant gas flows are off and the plasma is turned off.

ALD cycles 1110-1 are performed to deposit more silicon oxide materialafter etching in etch phase 1108-1. ALD cycles 1110-1 include repeatingoperations from ALD cycles 1102-1 such that ALD cycles 1110-1 includessilicon-containing precursor exposure phase 1102 a, purge phase 1102 b,oxidant exposure phase 1102 c, and purge phase 1102 d. Insilicon-containing precursor exposure phase 1102 a, argon is flowed as acarrier gas with silicon-containing precursor gas flow on, while oxidantand etchant flows are off and the plasma is turned off. In purge phase1102 b, argon gas remains on while silicon-containing gas, oxidant gas,and etchant gas flows are off and plasma is off. In oxidant exposurephase 1102 c, oxidant and purge gas flows are on, while plasma is turnedon and silicon-containing precursor and etchant gas flows are off. Inpurge phase 1102 d, argon gas is on while silicon-containing gas flow,oxidant gas flow, and etchant gas flows are off and plasma is turnedoff. While one ALD cycle is depicted, it will be understood thatmultiple cycles may be performed in some embodiments.

In this example, a combination of ALD cycles 1110-1 and PECVD exposure1110-2 are performed to deposit a second amount of silicon oxide afteretching in etch phase 1108-1. During PECVD exposure phase 1110-2, onlyone operation of PECVD exposure 1110 is depicted, whereby argon isflowed, silicon-containing precursor gas is flowed, oxidant gas isflowed, and a plasma is ignited to deposit silicon oxide. It will beunderstood that the silicon-containing precursor may be the same as ordifferent from the silicon-containing precursor used in ALD cycles1102-1 and 1110-1. PECVD exposure 1110-2 may correspond to formation ofa helmet on a field surface of a substrate.

In long etch back phase 1108-2, a longer duration of etching 1108 b isdepicted whereby argon is flowed, etchant gas is flowed, and plasma isignited to facilitate etching, while silicon-containing precursor andoxidant gas flows are turned off. This may correspond to opening of afeature opening by etching after forming a sacrificial helmet on thesubstrate.

Purge phase 1153 b involves flowing argon gas, while silicon-containinggas, oxidant gas, and etchant gas flows are turned off and plasma isoff. ALD cycles 1102-2 include repeating operations from ALD cycles1102-1 such that ALD cycles 1101-2 includes silicon-containing precursorexposure phase 1102 a, purge phase 1102 b, oxidant exposure phase 1102c, and purge phase 1102 d. In silicon-containing precursor exposurephase 1102 a, argon is flowed as a carrier gas with silicon-containingprecursor gas flow on, while oxidant and etchant flows are off and theplasma is turned off. In purge phase 1102 b, argon gas remains on whilesilicon-containing gas, oxidant gas, and etchant gas flows are off andplasma is off. In oxidant exposure phase 1102 c, oxidant and purge gasflows are on, while plasma is turned on and silicon-containing precursorand etchant gas flows are off. In purge phase 1102 d, argon gas is onwhile silicon-containing gas flow, oxidant gas flow, and etchant gasflows are off and plasma is turned off. While one ALD cycle is depicted,it will be understood that multiple cycles may be performed in someembodiments.

Apparatus

FIG. 12 depicts a schematic illustration of an embodiment of an atomiclayer deposition (ALD) process station 1200 having a process chamberbody 1202 for maintaining a low-pressure environment. Such station maybe used for performing certain disclosed embodiments, includingdeposition by ALD, PEALD, CVD, PECVD, as well as etch back operations. Aplurality of ALD process stations 1200 may be included in a common lowpressure process tool environment. For example, FIG. 13 depicts anembodiment of a multi-station processing tool 1300. In some embodiments,one or more hardware parameters of ALD process station 1200 includingthose discussed in detail below may be adjusted programmatically by oneor more computer controllers 1250.

ALD process station 1200 fluidly communicates with reactant deliverysystem 1201 a for delivering process gases to a distribution showerhead1206. Reactant delivery system 1201 a includes a mixing vessel 1204 forblending and/or conditioning process gases, such as ansilicon-containing precursor gas, or oxidant gas (e.g., oxygen ornitrous oxide), inert gases, etchant gases (e.g., nitrogen trifluoride)for delivery to showerhead 1206. One or more mixing vessel inlet valves1220 may control introduction of process gases to mixing vessel 1204.Nitrogen trifluoride and/or oxidant plasma may also be delivered to theshowerhead 1206 or may be generated in the ALD process station 1200.

As an example, the embodiment of FIG. 12 includes a vaporization point1203 for vaporizing liquid reactant to be supplied to the mixing vessel1204. In some embodiments, vaporization point 1203 may be a heatedvaporizer. The saturated reactant vapor produced from such vaporizersmay condense in downstream delivery piping. Exposure of incompatiblegases to the condensed reactant may create small particles. These smallparticles may clog piping, impede valve operation, contaminatesubstrates, etc. Some approaches to addressing these issues involvepurging and/or evacuating the delivery piping to remove residualreactant. However, purging the delivery piping may increase processstation cycle time, degrading process station throughput. Thus, in someembodiments, delivery piping downstream of vaporization point 1203 maybe heat traced. In some examples, mixing vessel 1204 may also be heattraced. In one non-limiting example, piping downstream of vaporizationpoint 1203 has an increasing temperature profile extending fromapproximately 100° C. to approximately 150° C. at mixing vessel 1204.

In some embodiments, liquid precursor or liquid reactant may bevaporized at a liquid injector. For example, a liquid injector mayinject pulses of a liquid reactant into a carrier gas stream upstream ofthe mixing vessel. In one embodiment, a liquid injector may vaporize thereactant by flashing the liquid from a higher pressure to a lowerpressure. In another example, a liquid injector may atomize the liquidinto dispersed microdroplets that are subsequently vaporized in a heateddelivery pipe. Smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 1203. In one scenario, a liquidinjector may be mounted directly to mixing vessel 1204. In anotherscenario, a liquid injector may be mounted directly to showerhead 1206.

In some embodiments, a liquid flow controller (LFC) upstream ofvaporization point 1203 may be provided for controlling a mass flow ofliquid for vaporization and delivery to process station 1200. Forexample, the LFC may include a thermal mass flow meter (MFM) locateddownstream of the LFC. A plunger valve of the LFC may then be adjustedresponsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC may bedynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, this may be performed by disabling asense tube of the LFC and the PID controller.

Showerhead 1206 distributes process gases toward substrate 1212. In theembodiment shown in FIG. 12, the substrate 1212 is located beneathshowerhead 1206 and is shown resting on a pedestal 1208. Showerhead 1206may have any suitable shape, and may have any suitable number andarrangement of ports for distributing process gases to substrate 1212.

In some embodiments, pedestal 1208 may be raised or lowered to exposesubstrate 1212 to a volume between the substrate 1212 and the showerhead1206. It will be appreciated that, in some embodiments, pedestal heightmay be adjusted programmatically by a suitable computer controller 1250.In some embodiments, the pedestal is powered and power may be applied togenerate a bias to the pedestal.

In another scenario, adjusting a height of pedestal 1208 may allow aplasma density to be varied during plasma activation cycles in theprocess in embodiments where a plasma is ignited. At the conclusion ofthe process phase, pedestal 1208 may be lowered during another substratetransfer phase to allow removal of substrate 1212 from pedestal 1208.

In some embodiments, pedestal 1208 may be temperature controlled viaheater 1210. In some embodiments, the pedestal 1208 may be heated to atemperature of between about 50° C. and about 650° C. In someembodiments, the pedestal is set at a temperature between about 50° C.and about 500° C., such as at a temperature between about 200° C. andabout 275° C. In some embodiments, the pedestal is set at a temperaturebetween about 50° C. and about 300° C. In some embodiments, the pedestalis set at a temperature between about 200° C. and about 275° C.

Further, in some embodiments, pressure control for process station 1200may be provided by butterfly valve 1218. As shown in the embodiment ofFIG. 12, butterfly valve 1218 throttles a vacuum provided by adownstream vacuum pump (not shown). However, in some embodiments,pressure control of process station 1200 may also be adjusted by varyinga flow rate of one or more gases introduced to the process station 1200.

In some embodiments, a position of showerhead 1206 may be adjustedrelative to pedestal 1208 to vary a volume between the substrate 1212and the showerhead 1206. Further, it will be appreciated that a verticalposition of pedestal 1208 and/or showerhead 1206 may be varied by anysuitable mechanism within the scope of the present disclosure. In someembodiments, pedestal 1208 may include a rotational axis for rotating anorientation of substrate 1212. It will be appreciated that, in someembodiments, one or more of these example adjustments may be performedprogrammatically by one or more suitable computer controllers 1250.

In some embodiments where plasma may be used as discussed above,showerhead 1206 and pedestal 1208 electrically communicate with a radiofrequency (RF) power supply 1214 and matching network 1216 for poweringa plasma. In some embodiments, the plasma energy may be controlled bycontrolling one or more of a process station pressure, a gasconcentration, an RF source power, an RF source frequency, and a plasmapower pulse timing. For example, RF power supply 1214 and matchingnetwork 1216 may be operated at any suitable power to form a plasmahaving a desired composition of radical species. Examples of suitablepowers are included above. Likewise, RF power supply 1214 may provide RFpower of any suitable frequency. In some embodiments, RF power supply1214 may be configured to control high- and low-frequency RF powersources independently of one another. Example low-frequency RFfrequencies may include, but are not limited to, frequencies between 0kHz and 500 kHz. Example high-frequency RF frequencies may include, butare not limited to, frequencies between 1.8 MHz and 2.45 GHz, or greaterthan about 13.56 MHz, or greater than 27 MHz, or greater than 40 MHz, orgreater than 60 MHz. It will be appreciated that any suitable parametersmay be modulated discretely or continuously to provide plasma energy forthe surface reactions. Plasma power may vary depending on whether thestation is performing deposition or etching. For example, exampleetching plasma powers include 1000 W to 5000 W.

In some embodiments, the plasma may be monitored in-situ by one or moreplasma monitors. In one scenario, plasma power may be monitored by oneor more voltage, current sensors (e.g., VI probes). In another scenario,plasma density and/or process gas concentration may be measured by oneor more optical emission spectroscopy sensors (OES). In someembodiments, one or more plasma parameters may be programmaticallyadjusted based on measurements from such in-situ plasma monitors. Forexample, an OES sensor may be used in a feedback loop for providingprogrammatic control of plasma power. It will be appreciated that, insome embodiments, other monitors may be used to monitor the plasma andother process characteristics. Such monitors may include, but are notlimited to, infrared (IR) monitors, acoustic monitors, and pressuretransducers.

In some embodiments, instructions for a controller 1250 may be providedvia input/output control (IOC) sequencing instructions. In one example,the instructions for setting conditions for a process phase may beincluded in a corresponding recipe phase of a process recipe. In somecases, process recipe phases may be sequentially arranged, so that allinstructions for a process phase are executed concurrently with thatprocess phase. In some embodiments, instructions for setting one or morereactor parameters may be included in a recipe phase. For example, afirst recipe phase may include instructions for setting a flow rate ofan inert and/or a reactant gas (e.g., the first precursor such as asilicon-containing precursor), instructions for setting a flow rate of acarrier gas (such as argon), and time delay instructions for the firstrecipe phase. A second, subsequent recipe phase may include instructionsfor modulating or stopping a flow rate of an inert and/or a reactantgas, and instructions for modulating a flow rate of a carrier or purgegas and time delay instructions for the second recipe phase. A thirdrecipe phase may include instructions for modulating a flow rate of asecond reactant gas such as oxygen, instructions for modulating the flowrate of a carrier or purge gas, and time delay instructions for thethird recipe phase. A fourth, subsequent recipe phase may includeinstructions for modulating or stopping a flow rate of an etchant gas,and instructions for modulating a flow rate of a carrier or purge gasand time delay instructions for the fourth recipe phase. A fifth recipephase may include instructions for modulating a flow rate of asilicon-containing gas as well as a nitrogen-containing oroxygen-containing gas for depositing a silicon nitride or oxide helmetrespectively, instructions for modulating the flow rate of a carrier orpurge gas, and time delay instructions for the fifth recipe phase. Itwill be appreciated that these recipe phases may be further subdividedand/or iterated in any suitable way within the scope of the disclosedembodiments. In some embodiments, the controller 1250 may include any ofthe features described below with respect to system controller 1350 ofFIG. 13.

As described above, one or more process stations may be included in amulti-station processing tool. FIG. 13 shows a schematic view of anembodiment of a multi-station processing tool 1300 with an inbound loadlock 1302 and an outbound load lock 1304, either or both of which mayinclude a remote plasma source. A robot 1306 at atmospheric pressure isconfigured to move wafers from a cassette loaded through a pod 1308 intoinbound load lock 1302 via an atmospheric port 1310. A wafer is placedby the robot 1306 on a pedestal 1312 in the inbound load lock 1302, theatmospheric port 1310 is closed, and the load lock is pumped down. Wherethe inbound load lock 1302 includes a remote plasma source, the wafermay be exposed to a remote plasma treatment in the load lock prior tobeing introduced into a processing chamber 1314. Further, the wafer alsomay be heated in the inbound load lock 1302 as well, for example, toremove moisture and adsorbed gases. Next, a chamber transport port 1316to processing chamber 1314 is opened, and another robot (not shown)places the wafer into the reactor on a pedestal of a first station shownin the reactor for processing. While the embodiment depicted in FIG. 13includes load locks, it will be appreciated that, in some embodiments,direct entry of a wafer into a process station may be provided.

The depicted processing chamber 1314 includes four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 13. Each stationhas a heated pedestal (shown at 1318 for station 1), and gas lineinlets. It will be appreciated that in some embodiments, each processstation may have different or multiple purposes. For example, in someembodiments, a process station may be switchable between an ALD andplasma-enhanced ALD process mode. Additionally or alternatively, in someembodiments, processing chamber 1314 may include one or more matchedpairs of ALD and plasma-enhanced ALD process stations. While thedepicted processing chamber 1314 includes four stations, it will beunderstood that a processing chamber according to the present disclosuremay have any suitable number of stations. For example, in someembodiments, a processing chamber may have five or more stations, whilein other embodiments a processing chamber may have three or fewerstations.

FIG. 13 depicts an embodiment of a wafer handling system 1390 fortransferring wafers within processing chamber 1314. In some embodiments,wafer handling system 1390 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 13 also depicts an embodiment of a system controller 1350 employedto control process conditions and hardware states of process tool 1300.System controller 1350 may include one or more memory devices 1356, oneor more mass storage devices 1354, and one or more processors 1352.Processor 1352 may include a CPU or computer, analog, and/or digitalinput/output connections, stepper motor controller boards, etc.

In some embodiments, system controller 1350 controls all of theactivities of process tool 1300. System controller 1350 executes systemcontrol software 1358 stored in mass storage device 1354, loaded intomemory device 1356, and executed on processor 1352. Alternatively, thecontrol logic may be hard coded in the controller 1350. ApplicationsSpecific Integrated Circuits, Programmable Logic Devices (e.g.,field-programmable gate arrays, or FPGAs) and the like may be used forthese purposes. In the following discussion, wherever “software” or“code” is used, functionally comparable hard coded logic may be used inits place. System control software 1358 may include instructions forcontrolling the timing, mixture of gases, gas flow rates, chamber and/orstation pressure, chamber and/or station temperature, wafer temperature,target power levels, RF power levels, substrate pedestal, chuck and/orsusceptor position, and other parameters of a particular processperformed by process tool 1300. System control software 1358 may beconfigured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components used to carry out variousprocess tool processes. System control software 1358 may be coded in anysuitable computer readable programming language.

In some embodiments, system control software 1358 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. Other computer software and/orprograms stored on mass storage device 1354 and/or memory device 1356associated with system controller 1350 may be employed in someembodiments. Examples of programs or sections of programs for thispurpose include a substrate positioning program, a process gas controlprogram, a pressure control program, a heater control program, and aplasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 1318and to control the spacing between the substrate and other parts ofprocess tool 1300.

A process gas control program may include code for controlling gascomposition (e.g., silicon-containing gases, oxidant gases, etchantgases, carrier gases, and purge gases as described herein) and flowrates and optionally for flowing gas into one or more process stationsprior to deposition in order to stabilize the pressure in the processstation. A pressure control program may include code for controlling thepressure in the process station by regulating, for example, a throttlevalve in the exhaust system of the process station, a gas flow into theprocess station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations inaccordance with the embodiments herein.

A pressure control program may include code for maintaining the pressurein the reaction chamber in accordance with the embodiments herein.

In some embodiments, there may be a user interface associated withsystem controller 1350. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 1350 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), etc. These parameters may be provided tothe user in the form of a recipe, which may be entered utilizing theuser interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 1350 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 1300.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 1350 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RF biaspower level, pressure, temperature, etc. The instructions may controlthe parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

The system controller 1350 will typically include one or more memorydevices and one or more processors configured to execute theinstructions so that the apparatus will perform a method in accordancewith disclosed embodiments. Machine-readable media containinginstructions for controlling process operations in accordance withdisclosed embodiments may be coupled to the system controller 1350.

In some implementations, the system controller 1350 is part of a system,which may be part of the above-described examples. Such systems caninclude semiconductor processing equipment, including a processing toolor tools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The system controller 1350, depending on theprocessing conditions and/or the type of system, may be programmed tocontrol any of the processes disclosed herein, including the delivery ofprocessing gases, temperature settings (e.g., heating and/or cooling),pressure settings, vacuum settings, power settings, radio frequency (RF)generator settings, RF matching circuit settings, frequency settings,flow rate settings, fluid delivery settings, positional and operationsettings, wafer transfers into and out of a tool and other transfertools and/or load locks connected to or interfaced with a specificsystem.

Broadly speaking, the system controller 1350 may be defined aselectronics having various integrated circuits, logic, memory, and/orsoftware that receive instructions, issue instructions, controloperation, enable cleaning operations, enable endpoint measurements, andthe like. The integrated circuits may include chips in the form offirmware that store program instructions, digital signal processors(DSPs), chips defined as application specific integrated circuits(ASICs), and/or one or more microprocessors, or microcontrollers thatexecute program instructions (e.g., software). Program instructions maybe instructions communicated to the system controller 1350 in the formof various individual settings (or program files), defining operationalparameters for carrying out a particular process on or for asemiconductor wafer or to a system. The operational parameters may, insome embodiments, be part of a recipe defined by process engineers toaccomplish one or more processing steps during the fabrication of one ormore layers, materials, metals, oxides, silicon, silicon dioxide,surfaces, circuits, and/or dies of a wafer.

The system controller 1350, in some implementations, may be a part of orcoupled to a computer that is integrated with, coupled to the system,otherwise networked to the system, or a combination thereof. Forexample, the system controller 1350 may be in the “cloud” or all or apart of a fab host computer system, which can allow for remote access ofthe wafer processing. The computer may enable remote access to thesystem to monitor current progress of fabrication operations, examine ahistory of past fabrication operations, examine trends or performancemetrics from a plurality of fabrication operations, to change parametersof current processing, to set processing steps to follow a currentprocessing, or to start a new process. In some examples, a remotecomputer (e.g. a server) can provide process recipes to a system over anetwork, which may include a local network or the Internet. The remotecomputer may include a user interface that enables entry or programmingof parameters and/or settings, which are then communicated to the systemfrom the remote computer. In some examples, the system controller 1350receives instructions in the form of data, which specify parameters foreach of the processing steps to be performed during one or moreoperations. It should be understood that the parameters may be specificto the type of process to be performed and the type of tool that thesystem controller 1350 is configured to interface with or control. Thusas described above, the system controller 1350 may be distributed, suchas by including one or more discrete controllers that are networkedtogether and working towards a common purpose, such as the processes andcontrols described herein. An example of a distributed controller forsuch purposes would be one or more integrated circuits on a chamber incommunication with one or more integrated circuits located remotely(such as at the platform level or as part of a remote computer) thatcombine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, an ALDchamber or module, an atomic layer etch (ALE) chamber or module, an ionimplantation chamber or module, a track chamber or module, and any othersemiconductor processing systems that may be associated or used in thefabrication and/or manufacturing of semiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the system controller 1350 might communicate with one ormore of other tool circuits or modules, other tool components, clustertools, other tool interfaces, adjacent tools, neighboring tools, toolslocated throughout a factory, a main computer, another controller, ortools used in material transport that bring containers of wafers to andfrom tool locations and/or load ports in a semiconductor manufacturingfactory.

An appropriate apparatus for performing the methods disclosed herein isfurther discussed and described in U.S. patent application Ser. No.13/084,399 (now U.S. Pat. No. 8,728,956), filed Apr. 11, 2011, andtitled “PLASMA ACTIVATED CONFORMAL FILM DEPOSITION”; and Ser. No.13/084,305, filed Apr. 11, 2011, and titled “SILICON NITRIDE FILMS ANDMETHODS,” each of which is incorporated herein in its entireties.

The apparatus/process described herein may be used in conjunction withlithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallyincludes some or all of the following operations, each operation enabledwith a number of possible tools: (1) application of photoresist on aworkpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curingof photoresist using a hot plate or furnace or UV curing tool; (3)exposing the photoresist to visible or UV or x-ray light with a toolsuch as a wafer stepper; (4) developing the resist so as to selectivelyremove resist and thereby pattern it using a tool such as a wet bench;(5) transferring the resist pattern into an underlying film or workpieceby using a dry or plasma-assisted etching tool; and (6) removing theresist using a tool such as an RF or microwave plasma resist stripper.

EXPERIMENTAL Experiment 1

An experiment was conducted on a substrate with a 15:1 feature having adepth of 5 microns with recessed tungsten and silicon oxide stubs andre-entrancy at the top of the feature near the feature opening.Conventional atomic layer deposition of silicon oxide over such asubstrate performed on the substrate, which resulted in voids where theoxide stubs come together on the sidewalls. Re-entrancy at the top ofthe feature also resulted in top voids. Another similar substrate wasexposed to 300 cycles of ALD, etch back using NF₃, multiple cycles ofALD, deposition of a helmet using PECVD for 60 seconds, a long etchback, and ALD deposition to fill the features. The substrate resulted inno voids, and no removal of material from the corners at the featureopening. These results suggested viability of certain discloseddep-etch-dep operations used for void-free gapfill of dielectricmaterial in high aspect ratio features with sidewall topography.

Experiment 2

An experiment was conducted on a substrate with recessed features havinga depth of 160 nm where the surface of the recessed features was siliconnitride where the feature opening at the top of the feature is 25 nm andthe sidewalls narrow depth wise to the bottom of the feature. Siliconoxide was deposited into the features using 40 cycles of ALD using anaminosilane precursor and N₂O/O₂ with plasma. Following ALD, a siliconoxide helmet was deposited by PECVD to a thickness of 125 Å. Afterhelmet deposition, the substrate was etched using NF₃ for a duration of32 seconds. The helmet was consumed entirely during the etch. SubsequentALD was performed to complete fill of the features. The feature wasfilled with little to no void formation.

An experiment was conducted on a substrate with recessed features havinga depth of 160 nm where the surface of the recessed features was siliconnitride where the feature opening at the top of the feature is 25 nm andthe sidewalls narrow depth wise to the bottom of the feature. Siliconoxide was deposited into the features using 40 cycles of ALD using anaminosilane precursor and N₂O/O₂ with plasma. Following ALD, a siliconnitride helmet was deposited by PECVD using an aminosilane precursor anda nitrogen plasma to a thickness of 125 Å. After helmet deposition, thesubstrate was etched using NF₃ for a duration of 32 seconds. Greaterthan 50% of the helmet remained after etch. Subsequent ALD was performedto complete fill of the features. Etch selectivity of the siliconnitride helmet to the silicon oxide deposited by ALD allowed for longeretch duration to open the feature.

An experiment was conducted on a substrate with recessed features havinga depth of 160 nm where the surface of the recessed features was siliconnitride where the feature opening at the top of the feature is 25 nm andthe sidewalls narrow depth wise to the bottom of the feature. Siliconoxide was deposited into the features using 40 cycles of ALD using anaminosilane precursor and N₂O/O₂ with plasma. Following ALD, a siliconnitride helmet was deposited by PECVD using an aminosilane precursor anda nitrogen plasma to a thickness of 65 Å. After helmet deposition, thesubstrate was etched using NF₃ for a duration of 32 seconds. The helmetwas consumed entirely during the etch. Subsequent ALD was performed tocomplete fill of the features. Due to the etch selectivity of thesilicon nitride helmet to the silicon oxide deposited by ALD, a thinnerhelmet was able to be used and still achieve void-free feature fill.

CONCLUSION

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

What is claimed is:
 1. A method of filling a feature on a substrate, themethod comprising: providing the substrate comprising the feature to aprocess chamber, the feature comprising a feature opening and sidewalls,the sidewalls having sidewall topography comprising stubs on a surfaceof the sidewall and regions between the stubs; depositing a first amountof silicon oxide into the feature conformally over the sidewalltopography for a duration insufficient to fill the feature using asilicon-containing precursor and an oxidant to form the first amount ofthe silicon oxide having the sidewall topography; exposing the firstamount of the silicon oxide to an etchant to etch some of the firstamount of the silicon oxide to smoothen the sidewall topography of thefirst amount of the silicon oxide and form an etched first amount of thesilicon oxide; and after etching the first amount of the silicon oxide,depositing a second amount of the silicon oxide over the etched firstamount of the silicon oxide.
 2. The method of claim 1, wherein the stubsof the surface prior to depositing the first amount of silicon oxidehave a dimension perpendicular to a planar surface of the sidewall ofbetween 20 Å and about 300 Å.
 3. The method of claim 1, wherein theduration insufficient to deposit the first amount of the silicon oxideinto the feature forms an overburden of silicon oxide on a field surfaceof the substrate.
 4. The method of claim 3, wherein exposing the firstamount of the silicon oxide to the etchant comprises preferentiallyetching the some of the first amount of the silicon oxide at or nearregions between the stubs at the feature opening relative to inside thefeature.
 5. The method of claim 1, wherein the second amount of thesilicon oxide is deposited by plasma-enhanced chemical vapor deposition.6. The method of claim 5, further comprising after depositing the secondamount of the silicon oxide, exposing the second amount of the siliconoxide to the etchant for a duration longer than the duration used forexposing the first amount of the silicon oxide to the etchant.
 7. Themethod of claim 1, wherein the sidewalls of the feature comprise two ormore materials layered in a stack.
 8. The method of claim 1, wherein thedepositing of the first amount of the silicon oxide and the exposing ofthe first amount of the silicon oxide to the etchant are performedwithout breaking vacuum.
 9. The method of claim 1, wherein the exposingof the first amount of the silicon oxide to the etchant and thedepositing of the second amount of the silicon oxide are performedwithout breaking vacuum.
 10. The method of claim 1, wherein the firstamount of the silicon oxide is deposited by one or more cycles of atomiclayer deposition, each cycle of atomic layer deposition comprisingalternating pulses of the oxidant and the silicon-containing precursor.11. The method of claim 10, wherein a plasma is ignited during pulses ofthe oxidant.
 12. The method of claim 1, wherein the etchant is selectedfrom the group consisting of nitrogen trifluoride, fluoroform (CHF3),octafluorocyclobutane (C4F8), tetrafluoromethane (CF4), and combinationsthereof.
 13. The method of claim 1, wherein the feature has a depth ofbetween about 0.5 microns and 6 microns.
 14. The method of claim 1,wherein the feature has an aspect ratio of at least 6:1.
 15. A method offilling a feature on a substrate, the method comprising: providing thesubstrate comprising the feature to a process chamber, the featurecomprising a feature opening and sidewalls, the sidewalls havingsidewall topography comprising stubs on a surface of the sidewall andregions between the stubs; depositing a first amount of silicon oxideinto the feature conformally over the sidewall topography for a durationinsufficient to fill the feature using a silicon-containing precursorand an oxidant to form the first amount of the silicon oxide having thesidewall topography; after depositing the first amount of silicon oxideand prior to exposing the first amount of silicon oxide to an etchant,depositing a sacrificial helmet forming an overburden on a field surfaceof the substrate; exposing the substrate to the etchant to etch some ofthe first amount of the silicon oxide to smoothen the sidewalltopography of the first amount of the silicon oxide and form an etchedfirst amount of the silicon oxide; and after etching the first amount ofthe silicon oxide, depositing a second amount of the oxide over theetched first amount of the silicon oxide to at least partially fill thefeature.
 16. The method of claim 15, wherein sacrificial helmet isdeposited by plasma enhanced chemical vapor deposition.
 17. The methodof claim 15, wherein the sacrificial helmet comprises silicon nitride orsilicon oxide.
 18. The method of claim 15, wherein the sacrificialhelmet comprises material different from the silicon oxide deposited inthe feature.
 19. The method of claim 5, further comprising afterdepositing the second amount of the silicon oxide, exposing the secondamount of the silicon oxide to the etchant for a duration shorter thanthe duration used for exposing the first amount of the silicon oxide tothe etchant.
 20. The method of claim 14, wherein the feature has anaspect ratio of at least 15:1.